The present invention relates to a composition for use in a dishwashing machine and a process for the use thereof.
Although modern dishwashing machines in most cases have numerous different washing programs, which differ with regards to the duration and temperature of the individual washing cycles, all washing programs essentially consist of the following basic steps: preliminary washing cycle, main cleaning cycle, one or more intermediate rinsing cycles, a clear rinsing cycle and drying. Whereas the machine dishwashing agent for bringing about the cleaning action is added at the start of the main cleaning cycle, during the clear rinsing cycle special agents are used, e.g. clear rinsing agents. Clear rinsing agents are intended to ensure that when washing with water water droplets are not left behind on the washed articles which, after drying on, leave behind marks of substances dissolved/dispersed in the droplets.
These two functionalities, namely the cleaning action of the machine dishwashing agent and the described function of a clear rinsing agent, have hitherto been brought about using two separate charging or dosing devices and products charged or dosed at different points during the dishwashing cycle.
Apart from the use of clear rinsing agents, there is still a need for further substances evolving their activity during the washing or rinsing cycle, such as e.g. an antibacterial activity (e.g. cationic compounds or triclosan), silver protection agents (e.g. benzotriazole), an odorous action (fragrances, perfume), bleaching action/disinfection (chlorine bleaches), odour masking (e.g. polyvinylpyrrolidone), anti-coating agents and enzymes for additional purposes (e.g. lipase for removing grease and fat deposits in the dishwasher). However, modern dishwashers have no suitable charging systems for this purpose.
The aim of the present invention was consequently to combine in a single function the cleaning function and the function or functions of the substance or substances to be added during the clear rinsing cycle with a constant efficiency compared with the results obtainable with a separate charging or to permit the charging of substances other than the clear rinsing agent in the clear rinsing cycle.
DE-OS 20 65 153 and 20 07 413 disclose detergent blanks for use as detergents, in which it is inter alia provided that two components having a different functionality are combined. The structure comprises an enveloping shell, which is e.g. formed from two shell halves comprising a cleaning agent, as well as a cavity enclosed by the shells and which contains additives such as softeners, brighteners, etc.
British patent 1 390 503 discloses a liquid detergent containing capsules, which are insoluble in the composition, but release their content if the composition is diluted with water. This objective is achieved in that the capsules are coated with a substance having a poor solubility in water solutions with high ionic strength, but becoming soluble if the ionic strength is reduced by dilution. It is pointed out that this procedure can be used to incorporate materials in the liquid cleaning agent, which are unstable in the latter or would produce an instability if added directly. It is also proposed that this procedure be used in order to delay the release of a specific substance. Reference is made to use in machine dishwashing agents and it is proposed for the encapsulation of tribromosalicylanilide in order to stabilize the latter. The encapsulated material is released within two minutes following the dilution of the cleaning agent with water, i.e. in the main cleaning cycle.
U.S. Pat. No. 4,082,678 describes a fabric conditioning product comprising a closed container containing a releasable agent, which is used to make water-insoluble or non-dispersible an inner container located in the container and which is normally water-soluble or water-dispersible, the inner container containing a fabric conditioner. The inner container is made from a substance, whose solubility in water is highly dependent on the ionic strength or the pH-value of the medium and the agent used for rendering the inner container insoluble is an agent for controlling the pH-value or ionic strength.
Japanese patent applications KOKAI 60-141705, 61-28440, 61-28441, 61-28596, 61-28597 and 61-28598 describe processes for the production of pH-sensitive microcapsules for use in detergents. The pH-sensitive coating is a copolymer of the following monomers:
A) at least one basic monomer of formula I: 
xe2x80x83in which R is hydrogen or a methyl group, R1 and R2 in each case an alkyl group with 1 to 3 carbon atoms and x an integer from 1 to 4,
B) at least one monomer, which is insoluble or difficultly soluble in water and
C) at least one water-soluble monomer.
It is stated that the polymers described are insoluble at a pH-value of 9.5 or higher and are soluble at a pH-value of 8.5 or lower. A description is given of different ingredients of cleaning agent compositions, which can be successfully and usefully coated with the polymers described. The aim of the invention described therein is that the substances only evolve their function during the rinsing cycle, protect the same up to the start thereof and then immediately release it. The use for dishwashing machines is not described.
A disadvantage of the solution described in these Japanese patent applications is that the enveloped particles are in direct contact with non-alkaline washing water at the start of the washing cycle which can lead to a partial dissolving of the protective envelope.
Japanese patent KOKAI 50-77406 discloses a washing aid surrounded by a water-soluble envelope obtained by mixing polyvinyl acetal dialkyl aminoacetate and at least one organic acid, which is solid at ambient temperature. This protective envelope serves to protect the washing aid during the main washing cycle and release it during rinsing cycles. The described compound reacts to a change of the pH-value between the main washing cycle and the rinsing cycle. The correspondingly enveloped particles are mixed with conventional pulverulent detergent. Here again the disadvantage of a possible partial dissolving of the protective envelope at the start of the washing cycle occurs.
European patent applications EP 284 191 A2 and 284 334 A2 disclose a water-soluble polymer film for the release of washing additives in the rinsing cycle of washing machines which, during the normal washing cycle, remains intact over a typical temperature range and rapidly dissolves in the rinsing cycle. It is pointed out that although the use of pH-sensitive coatings is known, said films are normally temperature-sensitive, so that they are not reliably stable during the different temperatures occurring in the washing cycle. The solution proposed is a pH-dependent material (which undesirably also has a positive temperature-dependent dissolving behaviour), which is combined with a material having a negative temperature-dependent dissolving behaviour. This combination is intended to guarantee that the coatings do not dissolve at the high temperatures at the start of the washing cycle (particularly the very high temperatures occurring in American machines). No reference is made to a use for machine dishwashing agents.
European patent application EP 481 547 A1 discloses multilayer machine dishwashing agent tablets with a core, a separating layer surrounding the core and an outer layer for the sequential release of the ingredients of the different layers. The aim of this tablet is to solve two different problems, namely 1) incompatible materials can be formulated together in a single tablet and released at different times in order to prevent mutual influencing and 2) compositions intended to evolve their functions at different times can be formulated in a single tablet.
One of the disadvantages of the prior art described in this document is that the only production process described is the successive moulding of the individual components. This leads to a risk of the core and/or core envelope being deformed, which can cause damage (and therefore a reduction of the protective action) of the core envelope and also (as a function of the core composition) can bring about a xe2x80x9cbleedingxe2x80x9d, of the core into the envelope material and basic composition. In addition, the intimate, full-surface contact between the individual layers can lead to undesired reactions occurring in the boundary layers, particularly between the envelope and the basic composition.
The second essential disadvantage of this prior art is that for initiating dissolving of the enveloping layer the temperature and in particular the contact time with the washing solution is used as the triggering factor, i.e. temperature-sensitive materials are used for the envelope material. As the temperature/time gradient in dishwashing machines can vary widely as a function of the program chosen, it is difficult, if not impossible, to select a material for the envelope usable for all possible programs of modern dishwashing machines. EP 481 547 A1 (p 7, lines 37 to 43) admits that the choice of the material for the enveloping layer must take account of equipment and program-specific features. Therefore the practical usability of the products described is clearly limited.
PCT application WO 95/29982 discloses a machine dishwashing agent with a delayed release of a clear rinsing agent in the form of a nonionic surfactant, which together with an inorganic builder salt forms a core particle, which is provided with a wax-like envelope in order to ensure the desired release. This envelope is a substance which does not melt at the operating temperatures encountered during the cleaning cycle, but chemically disintegrates under alkaline pH-values in a gradual manner so that there is still an effective clear rinsing agent quantity at the end of the main cleaning cycle and is transferred into the clear rinsing cycle.
It is disadvantageous that the envelope is rendered soluble by chemical saponification at alkaline pH-values, so that the time when the clear rinsing agent substance is released from the core is a function both of the temperature and the length of the main cleaning cycle. The patent application contains no teaching as to how a product is to be formulated with which the clear rinsing agent is released in the clear rinsing cycle in all washing programs of any equipment type. In addition, the core ingredient active as the clear rinsing agent is a nonionic surfactant, which is absorbed on an inorganic builder salt. This gives rise to inferior clear rinsing results, particularly mark and spot formation on glass. Finally the product is a mixture of a granular cleaning agent and granular clear rinsing agent particles.
In view of the prior art described, the problem of the present invention is to create a composition usable for most washing/rinsing programs of different dishwashing machine types and in each of these cases the substance or substances evolve their action essentially in the clear rinsing cycle, but are released at the earliest at the start of the clear rinsing cycle. The aim is to achieve this without significant restriction to the choice with respect to the cleaning agent chosen, the substance or substances used for the clear rinsing cycle and other ingredients of the composition.
According to the invention this problem is solved with a composition characterized by a basic composition, which evolves its function mainly in the main cleaning cycle of the dishwashing machine and which is in the form of a tablet, as well as at least one particle with at least one core incorporating at least one substance, which evolves its function essentially in the clear rinsing cycle of the dishwashing machine, and an envelope substantially completely surrounded by the core or cores, which incorporates at least one compound, whose solubility increases with decreasing concentration of a specific ion in the surrounding medium. The at least one particle is so arranged in or on the tablet that the surface of the particle or particles are at the most in partial direct contact with the surface of the basic composition surrounding the same and the concentration of the specific ion in the local environment of the particle or particles is sufficiently high up to a substantially complete dissolving of the tablet in order to prevent a significant dissolving of the envelope or a significant detachment of the envelope from the core or cores.
Preferably the or all particles are received in at least one tablet cavity completely surrounded by the basic composition and which has a larger volume than the or all the particles received in the particular cavity.
In an alternative, the particle or particles can be loosely arranged in the interior of the cavity or, in another alternative, can be fixed. In the case of fixing in the interior of the cavity this preferably takes place by an adhesive.
In a particularly preferred embodiment of the invention the cavity is arranged substantially centrally in the tablet interior.
According to the invention the tablet has a single, substantially spherical cavity, in which is received a single, substantially spherical particle, whose external diameter is smaller than the internal diameter of the cavity.
In an alternative embodiment of the invention the particle or all the particles are received in at least one tablet cavity only partly surrounded by the basic composition.
The cavity is preferably a depression in one of the tablet surfaces in which the particle or particles are at least partly received.
The particle or particles are preferably received in the cavity or depression in such a way that they do not project over the tablet surface or surfaces.
According to an embodiment of the invention the cavity or depression, parallel to one of the surfaces to which it opens or in which it is located, has a substantially circular cross-sectional surface.
According to a special embodiment of the invention the cavity or depression only opens towards the surface or surfaces to the extent that the particle or particles received therein cannot pass through the opening or openings of the cavity or depression.
Preferably the particle or particles are arranged in the cavity or depression in loose form.
However, it is also possible for the particle or particles to be fixed in the cavity or depression, said fixing preferably taking place with an adhesive.
Preferably, according to the invention, the basic composition incorporates at least one composition selected from the group comprising a machine dishwashing composition, a water softener composition and a washing intensifier composition.
Preferably, according to the invention, the envelope incorporates at least one compound which is not or only slightly soluble at the concentration of the specific ion at the end of the main cleaning cycle of the dishwashing machine and in which the concentration of the specific ion in the clear rinsing cycle has an adequate solubility such that it is so substantially dissolved or detached from the core or cores in the clear rinsing cycle that an at least partial escape of the core material into the clear rinsing cycle medium is rendered possible.
Preferably the solubility of the compound increases with decreasing OHxe2x88x92 ionic concentration and therefore decreasing pH-value in the surrounding medium.
According to a particularly preferred embodiment of the invention, the compound has no or only a limited solubility at a pH-value above 10 and at a pH-value below 9 has an adequate solubility so that in the clear rinsing cycle it is substantially dissolved or detached from the core or cores in such a way that there is an at least partial escape of the core material into the clear rinsing cycle medium.
Said compound preferably incorporates a polymer and in particularly preferred manner a pH-sensitive polymer, which has at least one repeat unit, which has at least one basic function, which is not part of the polymer backbone chain.
In a preferred embodiment the polymer has at least one repeat unit based on a compound selected from the group comprising vinyl alcohol derivatives, acrylates or alkyl acrylates, having said basic function.
In a special embodiment of the invention the polymer is a carbohydrate functionalized with said basic function.
The aforementioned basic function is preferably an amine, preferably a secondary or tertiary amine.
In an alternative the repeat unit is based on a compound with the following formula III: 
in which G is a linking group chosen from xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94CONHxe2x80x94, xe2x80x94NHCOxe2x80x94, xe2x80x94NHCONHxe2x80x94, xe2x80x94NHCOOxe2x80x94, xe2x80x94OCONHxe2x80x94 or xe2x80x94OCOOxe2x80x94, R1 independently of one another is hydrogen or an alkyl group with 1 to 3 carbon atoms, R2, independently of one another, hydrogen or an alkyl group with 1 to 5 carbon atoms and x an integer from 1 to 6.
The repeat unit is preferably based on a compound with the following formula IV: 
in which R1, independently of one another, is hydrogen or an alkyl group with 1 to 3 carbon atoms, R2, independently of one another, hydrogen or an alkyl group with 1 to 5 carbon atoms and x an integer from 1 to 6.
According to another embodiment of the invention the basic function is an imine or a basic aromatic N-containing group, preferably a pyridine group or an imidazole group.
In a further embodiment the pH-sensitive polymer is derived from chitosan.
The invention finally proposes that the compound incorporates K-carrageenan.
According to an embodiment of the invention the core or cores comprise at least one material chosen from the group consisting of surfactants, antibacterial compositions, silver protection agents, fragrances, bleaches, disinfectants, odour masking agents, anti-coating agents and enzymes.
In an alternative the core or at least part of the cores can be in the form of encapsulated liquid, e.g. in the form of a liquid contained in a gelatin capsule.
In an alternative embodiment the core or at least part of the cores is in solid form and preferably has a melting point of more than 35xc2x0 C., particularly preferred temperatures being 55 to 70xc2x0 C.
The invention also relates to a process for performing a dishwashing cycle in a dishwashing machine, where the composition according to the invention is added at an appropriate time during the preliminary washing cycle or the main cleaning cycle to the medium present in the dishwashing machine.
In a special embodiment of this process, for the case that the basic composition in the form of a tablet is unable following its dissolving in the medium to make available up to the end of the main cleaning cycle a concentration of the specific ion in the medium which is sufficiently high to prevent a significant dissolving of the envelope and a significant detachment of the envelope from the core or cores, said adequate concentration of the specific ion is provided by the addition of a further composition, such as e.g. a machine dishwashing agent composition, to the medium of the main cleaning cycle at an appropriate time.
The composition according to the invention is characterized in that it gives excellent results both in the main cleaning cycle and in the clear rinsing cycle of a dishwashing machine. The tablet is dissolved during the main cleaning cycle and can evolve its corresponding, intended action (cleaning, water softening, washing intensifying, etc.). The particle located in or on the tablet contains as the core material the substance or substances intended to evolve their main function in the clear rinsing cycle of the dishwashing machine, e.g. clear rinsing agents.
Said substance or substances are protected by an envelope, which is stable at the ionic concentration, e.g. the pH-value and the temperature of the main cleaning cycle and which do not or do not significantly dissolve or separate. Only if the ionic concentration or pH-value drops significantly by dilution, i.e. at the start of the clear rinsing cycle, is the solubility of the enveloping material reduced to such an extent that it rapidly dissolves or separates and releases the active core material into the surrounding medium.
If special dosing or charging aids are not provided for dosing or charging purposes and which can retain the particles according to the invention, said particles are to be chosen sufficiently large that they are not discharged to a significant extent during the pumping out after the main cleaning cycle and the intermediate rinsing cycle or cycles from the dishwashing machine.
For the solution according to the invention it is essential that the particle surface is at the most only in partial direct contact with the surface of the basic composition of the tablet surrounding it. This can take place in manner specifically described in this application, but also in any other way achieving the aim in question. Examples are the loose arrangement of a smaller particle in a larger cavity and the fixing of a smaller particle in a larger cavity in such a way that there is no or only a partial contact between the particle and the basic composition of the tablet, etc.
Compared with the prior art this procedure offers the advantage that during the production process, e.g. the moulding of the individual ingredients occurring in successive steps, a deformation and possibly a therefrom resulting damage to the core or cores and/or envelope is reliably avoided, because it could give rise to a reduction of the protective action of the core envelope. Through avoiding pressure being exerted on the particle during any phase of the production process, it is also possible to ensure that for a specific core composition there is no xe2x80x9cbleedingxe2x80x9d thereof into the material of the envelope and the basic composition. In addition, for specific core compositions or the base composition it can be advantageous to avoid an intimate, full surface contact, because otherwise undesired reactions could occur in the boundary layers.
The term xe2x80x9clocal environmentxe2x80x9d, as used in the context of the particle according to the invention, is intended to designate the direct environment around said particle. The ionic concentration in this local environment of the particle is the determinative factor for its stability. In the case of the products according to the invention the ionic concentration in said local environment, at least up to a substantially complete dissolving of the tablet, is determined by ions dissolving therein. Preferably the origin of the xe2x80x9cspecific ionxe2x80x9d is, at least in the initial phase of the main cleaning cycle, a compound from the tablet-forming basic composition or is produced by it in the surrounding medium. In the most typical case for conventional basic dishwashing agents it consists of OHxe2x88x92 ions, whose concentration can be expressed as a pH-value.
If the basic composition is not constituted by an e.g. basic machine dishwashing agent composition, but instead e.g. a water softener composition or washing intensifier composition, the protection of the particle envelope by a sufficiently high ionic concentration in the local environment of the particle is possibly only ensured until the tablet has completely dissolved, namely in cases where the basic composition of the tablet is unable to provide a sufficiently high ionic concentration in the medium. In these cases the sufficiently high ionic concentration in the medium (and therefore also in the local environment of the particle or particles) is brought about by dissolving the machine dishwashing agent (or a further specific additive).